The present invention relates to techniques for sorting objects by color.
Sorters with a single color camera, known as monochromatic sorters, detect light intensity variations reflected from objects being sorted. By varying the color of the lighting system, the camera can distinguish between a limited range of colors and shades within a color. However, a single color camera cannot effectively sort objects where the color variation between an object that should be accepted and an object that should be rejected is in more than one color domain.
Sorters with a multiple color camera system are used to sort objects which have colors in more than one color domain. Multiple color sorters traditionally use two or three different monochromatic cameras measuring the absolute light intensity reflectance from objects at two or three different colors, respectively. Red, green, and blue colors are frequently used because any color can be defined in terms of its red, green and blue color content.
What is desired, therefore, is a color sorting system based, at least in part, on the hue of an object so that operators may easily adjust the sorting criteria. The hue values should extend beyond the red to green color range in order to sort objects encompassing a broader color range. In addition, color saturation values and, in some cases, intensity values should preferably be used to enhance color recognition. The color sorting system should also be insensitive to light intensity variations. The speed and number of objects capable of being sorted should be maximized, while simultaneously minimizing errors from rotational movement of objects between cameras. Further, the sorting system should be capable of detecting small blemishes and enhancing the appropriate colors.
The foregoing and other objectives, features, and advantages of the invention may be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings.